Method for determining the step size for an LMS adaptive equalizer for 8VSB

Abstract

A method and system for determining a step size of an adaptive equalizer for a digital data receiver. The data received by the receiver includes coded symbols and uncoded symbols. The method includes determining a first error estimate based on decoded symbols corresponding to the coded symbols, determining a second error estimate based on the uncoded symbols, adaptively selecting the first error estimate or the second error estimate based on a convergence criterion, and determining a step size based on the selected error estimate.

1. A method of determining a step size of an adaptive equalizer for a digital data receiver, data received by the receiver including coded symbols and uncoded symbols, the method comprising:
 determining a first error estimate based on decoded symbols corresponding to the coded symbols; 
 determining a second error estimate based on the uncoded symbols; 
 comparing the first error estimate to an error estimate threshold value; 
 continuously adaptively selecting one of the determined first error estimate and the determined second error estimate based on the comparison to the error estimate threshold value, 
 wherein, when the first error estimate is less than the error estimate threshold value, the first error estimate is selected, and when the first error estimate is greater than the error estimate threshold value, the second error estimate is selected, and 
 wherein, when no uncoded symbols are available to determine the second error estimate, a previously calculated value for the second error estimate is used for the adaptive selection of one of the determined first error estimate and the determined second error estimate; and 
 determining a step size based on the selected error estimate. 
 
     
     
       2. The method of  claim 1 , wherein the coded symbols are trellis-coded 8-level symbols. 
     
     
       3. The method of  claim 1 , further comprising decoding the coded symbols to produce the decoded symbols. 
     
     
       4. The method of  claim 3 , wherein the coded symbols are decoded with a zero delay. 
     
     
       5. The method of  claim 1 , wherein the first error estimate is a mean-squared-error estimate. 
     
     
       6. The method of  claim 5 , wherein the first error estimate is an averaged mean-squared-error estimate determined based on a plurality of instantaneous mean-squared-error estimates. 
     
     
       7. The method of  claim 1 , wherein the uncoded symbols comprise 2-level segment sync symbols, the method further comprising slicing the 2-level symbols. 
     
     
       8. The method of  claim 7 , wherein the second error estimate is determined based on the sliced 2-level symbols. 
     
     
       9. The method of  claim 1 , wherein determining a step size based on the selected error estimate comprises:
 comparing the selected error estimate with a plurality of error ranges including a first error range, each of the error ranges having a corresponding step size; and 
 selecting the corresponding step size of the first error range if the selected error estimate is within the first error range. 
 
     
     
       10. The method of  claim 1 , wherein the error estimate threshold value comprises one of a predetermined mean-squared-error and a predetermined signal to noise plus interference ratio, and wherein the second error estimate is selected when the first error estimate is equal to the error estimate theshold value. 
     
     
       11. The method of  claim 1 , wherein the equalizer is a linear-mean-squared (LMS) equalizer for 8-level-vestigial-sideband (8VSB) modulated signals. 
     
     
       12. The method of  claim 1 , wherein the method is iteratively performed. 
     
     
       13. The method of  claim 1 , wherein the digital data receiver is a digital television receiver. 
     
     
       14. A method of determining a step size of an adaptive equalizer for a digital data receiver, data received by the receiver including coded symbols and uncoded symbols, the method comprising:
 based on a convergence criterion, selecting one of a first signal estimation process and a second signal estimation process, the first signal estimation process utilizing decoded symbols corresponding to the coded symbols, and the second signal estimation process utilizing the uncoded symbols; 
 determining a signal estimate based on the selected signal estimation process; 
 determining an error estimate based on the received data and the signal estimate; and 
 determining a step size based on the error estimate by comparing the error estimate with a plurality of error ranges including a first error range, each of the error ranges having a corresponding step size, and selecting the corresponding step size of the first error range if the error estimate is within the first error range. 
 
     
     
       15. The method of  claim 14 , wherein the convergence criterion is indicative of a signal to noise plus interference ratio. 
     
     
       16. The method of  claim 14 , wherein the decoded symbols are trellis decoded symbols, and the uncoded symbols are segment sync symbols. 
     
     
       17. The method of  claim 14 , wherein the error estimate is a mean-squared-error estimate. 
     
     
       18. The method of  claim 14 , wherein the digital data receiver is a digital television receiver. 
     
     
       19. An adaptive equalizer for a digital data receiver, data received by the receiver including coded symbols and uncoded symbols, the equalizer comprising:
 a selection module configured to continually select, based on a convergence criterion, one of decoded symbols and the uncoded symbols, the decoded symbols corresponding to the coded symbols; 
 an error estimator configured to compare the received data and the selected symbols, and to generate an error estimate based on the comparison; and 
 a step size generator configured to generate a step size based on the error estimate, wherein the step size generator comprises a comparator configured to compare the error estimate with a plurality of error ranges including a first error range, each of the error ranges having a corresponding step size, and to select the corresponding step size of the first error range if the error estimate is within the first error range. 
 
     
     
       20. The equalizer of  claim 19 , wherein the equalizer is implemented on a semiconductor chip. 
     
     
       21. The equalizer of  claim 19 , wherein the coded symbols are trellis-coded symbols, further comprising a trellis decoder configured to decode the coded symbols to produce the decoded symbols. 
     
     
       22. The equalizer of  claim 19 , wherein the error estimate comprises a mean-squared-error estimate. 
     
     
       23. The equalizer of  claim 19 , wherein the uncoded symbols comprise segment sync symbols, the equalizer further comprising a slicer configured to slice the segment sync symbols to produce sliced uncoded symbols. 
     
     
       24. The equalizer of  claim 23 , wherein the selection module is configured to select, based on the convergence criterion, one of the decoded symbols and the sliced uncoded symbols. 
     
     
       25. The equalizer of  claim 19 , wherein the convergence criterion comprises one of a predetermined mean-squared-error and a predetermined signal to noise plus interference ratio. 
     
     
       26. The equalizer of  claim 19 , wherein the equalizer is implemented in a digital television receiver. 
     
     
       27. A device configured to process digital television signals, the device comprising:
 a receiver including a demodulator, a decoder, a slicer, and an equalizer, 
 the receiver configured to receive radio frequency signals modulated with data including coded symbols and uncoded symbols, 
 the demodulator configured to demodulate the received radio frequency signals to produce the coded symbols and the uncoded symbols, 
 the decoder configured to decode the coded symbols to produce corresponding decoded symbols, 
 the slicer configured to slice the uncoded symbols to produce corresponding sliced symbols, and 
 the equalizer including
 a selection module configured to select, based on a convergence criterion, one of the decoded symbols and the sliced symbols, 
 an error estimator configured to compare the data and the selected symbols, and to generate an error estimate based on the comparison, and 
 a step size generator configured to generate a step size based on the error estimate. 
 
 
     
     
       28. The device of  claim 27 , wherein the device is a tuner, a television, a PC adapter card, a set top box, a DVD recorder, a HDTV recorder, a phone, or a handheld device. 
     
     
       29. A method of determining a step size for a linear-mean-squared (LMS) equalizer of 8-level-vestigial-sideband (8VSB) modulated signals having trellis-coded symbols and segment sync symbols, the method comprising:
 (a) decoding the trellis-coded symbols; 
 (b) determining a first mean-squared-error estimate based on the decoded trellis-coded symbols; 
 (c) slicing the segment sync symbols; 
 (d) determining a second mean-squared-error estimate based on the sliced segment sync symbols; 
 (e) comparing the first mean-squared-error estimate to an error estimate threshold value; 
 (f) continually adaptively selecting one of the first mean-squared-error estimate and the second mean-squared-error estimate based on the comparison to the error estimate threshold value,
 wherein, when the first mean-squared-error estimate is less than the error estimate threshold value, the first mean-squared-error estimate is selected, and when the first mean-squared-error estimate is greater than or equal to the error estimate threshold value, the second mean-squared-error estimate is selected, and 
 wherein, when no uncoded symbols are available to determine the second mean-squared-error estimate, a previously calculated value for the second mean-squared-error estimate is used for the adaptive selection of one of the determined first mean-squared-error estimate and the determined second mean-squared-error estimate; 
 
 (g) determining a step size based on the selected error estimate; and 
 (h) iteratively performing acts (a)-(g). 
 
     
     
       30. A digital communication receiver configured to receive radio frequency signals modulated with data including coded symbols and a priori known uncoded symbols, the receiver comprising:
 a demodulator configured to demodulate the received radio frequency signals to produce the coded symbols and the a priori known uncoded symbols; 
 a decoder configured to decode the coded symbols to produce corresponding decoded symbols; and 
 an equalizer including
 a selection module configured to select, based on a convergence criterion, one of the decoded symbols and the a priori known uncoded symbols, 
 an error estimator configured to compare the data and the selected symbols, and to generate an error estimate based on the comparison, and 
 a step size generator configured to generate a step size based on the error estimate.